The present invention relates to a skin electrode for diagnostic purposes. More particularly, it relates to an improvement of a skin electrode for operatively connecting monitoring equipment to the surface of the skin to be monitored which is separable into two assemblies; a base assembly adapted to be mounted to the surface of the skin and having a sensing element for detecting biopotentials from the surface of the skin and transforming them into electrical signals, and; a terminal assembly adapted to be releasably coupled with the base assembly and having a lead for connection to the monitoring equipment for the transmission of the electrical signals.
When organs or tissues of a living body are excited, weak biopotentials are created. It is a widely known practice to transform such biopotentials into electrical signals which are monitored for diagnostic purposes by means of instruments, such as electrocardiographs and electroencephalographs. As the biopotentials are very weak, for example, on the order of 2 millivolts, the state of contact between the surface of the skin to be monitored and the sensing element significantly affects the readout results and, if it is not appropriate, unacceptable errors are invited. Accordingly, it is a usual practice to apply an electrolyte gel between the sensing element of the skin electrode and the surface of the skin so as to reduce contact resistance between them and to minimize variations in the accuracy of the electrode readout.
Known is a skin electrode comprising: a base assembly adapted to be mounted to the surface of the skin to be monitored and having a sensing element for detecting biopotentials from the surface of the skin and transforming them into electrical signals, and; a terminal assembly adapted to be releasably coupled with the base assembly and having a lead for connection to the monitoring equipment for the transmission of the electrical signals. For electrical connection of the base and terminal assemblies together, use has heretofore been made of a jack-plug, clip, of snap-hook type connection. Typically, the base assembly includes a male connector adapted to be snapped into a female connector provided in the terminal assembly. The force required for snapping into place such male and female connectors often causes the electrolyte gel applied between the base assembly and the surface of skin to leak out from the skin area to be monitored. Such leaking-out of the gel invites the following inconveniences.
(1) The effective area of the surface of the skin from which biopotentials are taken out varies.
(2) The effective site of the skin is displaced and, thus, the accuracy of signals is lowered.
(3) The base assembly normally includes a flexible plastic disc having a side toward the surface of the skin coated with a pressure-sensitive adhesive, by which the base assembly may be securely mounted to the surface of the skin. If the electrolyte gel is forced to be present between the disc and the surface of skin, the adhesion eventually becomes so poor that the secure mounting of the base assembly to the surface of skin is not ensured.
(4) If the electrolyte gel which has leaked out comes into contact with undesired parts of the base assembly, the signals transmitted to the monitoring equipment include perturbations resulting in misdiagnosis.
Thus, with such prior art skin electrodes, the connection of the base and terminal assemblies can only be safely performed by a person well trained in that operation.